The Nigerian frontman joined Saints in January, but failed to make his mark in England and was not given more than four starts during the rest of the season.
Onuachu was keen to move on following Southampton’s relegation and Trabzonspor won the race for his signature on a loan deal.
He has been impressive so far in his ongoing loan spell as he has already made five-goal contributions in his seven league starts.
The 29-year-old forward scored on Saturday against Fenerbahce where Trabzonspor won the match by a 3-2 scoreline.
According to Turkish daily Sabah, the Nigerian striker earned a big bonus for scoring and helping Trabzonspor beat Fenerbahce last week.
It has been suggested that a delighted club president Ertugrul Drogan, following the victory, awarded the players and the staff £143,000 (5m Turkish Lira) in bonus prize money, which is double the usual bonus.
Now it remains to be seen if Onuachu will return to St. Mary’s at the end of the current campaign after experiencing a dry spell with the Saints.
